Transient receptor potential (TRP) channels are non-selective cation channels that are activated by a variety of physical (e.g., temperature, osmolarity, mechanical) and chemical stimuli. A subset of the TRP channel superfamily is thermoresponsive, each channel being activated over a discrete temperature range, cumulatively spanning from noxious cold to noxious heat. TRP melastatin 8 (TRPM8) belongs to the melastatin subgroup of the TRP channel superfamily. TRPM8 is sensitive to cold temperature and menthol, and therefore also called as cold menthol receptor-1 (CMR-1) (e.g., Nonpatent Document 1). TRPM8 is known to be stimulated by cool to cold temperatures (8 to 28° C.) as well as by chemical substances such as menthol and icilin.
TRPM8 is located on primary nociceptive neurons (A-δ and C-fibers) and is also modulated by inflammation-mediated second messenger signals (e.g., Nonpatent Document 2 and 3). The location of TRPM8 on both A-δ and C-fibers may provide a basis for abnormal cold sensitivity in pathologic conditions wherein these neurons are altered, resulting in pain, often of a burning nature. TRPM8 immunostaining in primary afferents was increased in rats with chronic constriction injury (CCI), a neuropathic pain model manifesting cold allodynia in hindlimbs (e.g., Nonpatent Document 4). The expression of TRPM8 in primary afferents was increased in oxaliplatin-induced cold allodynia model in mice (e.g., Nonpatent Document 5).
Cold intolerance and paradoxical burning sensations induced by chemical substances or thermal cooling closely parallel symptoms seen in a wide range of clinical disorders and thus provide a strong rationale for the development on TRPM8 modulators as novel antihyperalgesic or antiallodynic agents. TRPM8 is also known to be expressed in the brain, lung, bladder, gastrointestinal tract, blood vessels, prostate and immune cells, thereby providing the possibility for therapeutic modulation in a wide range of maladies.
N-Benzothiopheneylsulfonamide compounds (e.g., Patent Document 1), N-benzimidazolylsulfonamide compounds (e.g., Patent Document 2), N-phenylsulfonamide compounds, N-pyridylsulfonamide compounds (e.g., Patent Document 3), etc. have been known as a TRPM8 modulator. However, it has never been reported that a compound wherein the compound has a bicyclic aromatic heterocycle comprised of pyridine condensed with benzene or of pyridine condensed with monocyclic aromatic heterocycle and the bicyclic aromatic heterocyle binds to a sulfonylamino moiety has TRPM8 antagonistic activity.    [Patent document 1] WO 2009/012430 pamphlet    [Patent document 2] WO 2010/144680 pamphlet    [Patent document 3] WO 2010/125831 pamphlet    [Nonpatent document 1] D. D. McKemy, and other two persons, “Identification of a cold receptor reveals a general role for TRP channels in thermosensation”, Nature, 2002, Vol. 416, No. 6876, p. 52-58    [Nonpatent document 2] J. Abe, and other four persons, “Ca2+-dependent PKC activation mediates menthol-induced desensitization of transient receptor potential M8”, Neuroscience Letters, 2006, Vol. 397, No. 1-2, p. 140-144    [Nonpatent document 3] L. S. Premkumar, and other four persons, “Downregulation of Transient Receptor Potential Melastatin 8 by Protein Kinase C-Mediated Dephosphorylation”, The Journal of Neuroscience, 2005, Vol. 25, No. 49, p. 11322-11329    [Nonpatent document 4] H. Xing, and other four persons, “TRPM8 Mechanism of Cold Allodynia after Chronic Nerve Injury”, The Journal of Neuroscience, 2007, Vol. 27, No. 50, p. 13680-13690    [Nonpatent document 5] P. Gauchan, and other three persons, “Involvement of increased expression of transient receptor potential melastatin 8 in oxaliplatin-induced cold allodynia in mice”, Neuroscience Letters, 2009, Vol. 458, No. 2, p. 93-95